In generally, the organic thin film transistor (OTFT) is manufactured by the material of conjugated polymers or organic small molecular materials. Comparing with inorganic transistor, the organic thin film transistor can be manufactured at low temperature, so we can select the plastic with light, thin, and cheap to replace the glass substrate. Furthermore, the processes of OTFT are simpler, and using high precision printing to pattern organic thin film can reduce the number of masks and vacuum evaporation equipments. The processes of OTFT are suitable for a plastic substrate, so that it suitable for a roll to roll process in the future and it can also reduce the cost of manufacturing thin film transistor.
In 2003, Royal Philips Electronics disclosed that manufacturing OTFT-EPD by using the soluble pentacene, wherein the device of OTFT is formed on a plastic substrate, and it is a Bottom-Contact/Bottom-Gate structure, and the material of the electrode (gate/source/drain) is Au, and using shadow mask process to form the electrode (gate/source/drain), and using the spin coating to form semiconductor layer with the soluble pentacene.
In summary, the conventional method for manufacturing an organic thin film transistor exists at least the following shortcomings:    1. The conventional method adopts the shadow mask process to form the electrode and spin coating to form semiconductor layer such that the cost of equipments required in the process is increased and thus the competitiveness is decreased.    2. The conventional method for manufacturing an organic thin film transistor uses shadow mask process to form the electrode to be reducing the solution of conducting wire, making a shorting of electrode, and increasing difficult of conducting line design.    3. The conventional method for manufacturing an organic thin film transistor may cause an environmental problem, since the soluble pentacene used in the conventional method had to be dissolved in the chloroform that is the most industry country prohibited.